MINNEAPOLIS (WCCO) — The National Transportation Safety Board says weather was a major factor in September’s medical helicopter crash in Alexandria, which seriously injured three people.

Officials say a North Memorial Medical Center helicopter was flying from Brainerd Lakes Regional Airport to Douglas County Hospital just after 2 a.m. on Sept. 17. There was one pilot and two crew members aboard.

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The NTSB says the helicopter lost contact with air traffic control halfway on its journey. Clouds started forming beneath the aircraft, creating a challenge for landing.

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The helicopter missed the approach while beginning to land in Alexandria and banked left to right, eventually colliding with tall trees before crashing on Chandler Field Airport near the hospital.

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The crew members were hospitalized in critical condition. Two have been released since the crash.